1. Field of the Invention
The invention relates to a process for pressure checking a hollow body section.
2. Description of the Prior Art
Hollow body sections are subjected to a bursting test to check their brittle fracture resistance and/or material properties. For this purpose, the two open ends are closed by bottoms and provided with a filling-and-emptying connection. After the interior is filled with a fluid, the pressure is increased by means of a pump until bursting occurs. The circumferential strain, fracture area formation and, if required, bursting pressure are then evaluated. For the serial inspection of hollow body sections, such, for example, as airbag tubes, the process is very complex and time-consuming. Moreover, this conventional process cannot simulate a dynamic internal pressure load.
JP 58-167937 (A) in "Pat. Abstr. of Japan, Sect. P, Vol. 8 (1984) No. 1 (P-246)" discloses a process for pressure checking a hollow body section. One end of the test item stands on an abutment, while a piston of a hydraulic cylinder engages into the opposite open end. The hollow space of the test item is filled with soft rubber, and piston-like sealing rings of hard rubber are placed at the top and bottom to prevent the soft rubber from flowing off in the gap between the interior surface of the test item and the piston of the hydraulic cylinder. Pressure is applied to the piston-cylinder unit to produce an axial force on the soft rubber. This axial force creates an internal pressure in the test item, which pressure is increased until a plastic flow occurs. The material characteristic values that result are then found. Dynamic component checking is not possible with this arrangement, because the soft rubber has high compressibility and viscosity compared with a liquid. Nor can high load application speeds be produced with a hydraulic piston-cylinder unit. It is also disadvantageous that the soft rubber becomes brittle at low testing temperatures.
DE 3504685 C2 discloses a process and a device for checking the internal pressure of a tube, especially a protecting tube. The protecting tube to be checked is clamped tightly at both ends in a testing device that resembles a turning machine. A cylindrical filling piece and, at a distance therefrom, a plug are inserted into the hollow space of the protecting tube. Because the external diameter of the plug is somewhat smaller than the internal diameter of the protecting tube, a continuous annular gap is created. The plug, which extends through the left end piece, is suddenly moved in the direction of the protecting tube by a suitable hydraulic device, so that a pressure of up to 80,000 bar is built up in the liquid enclosed between the filling piece and the plug. This pressure is reduced via the annular gap along the protecting tube to the previously applied precompression of approximately 200 bar. This process allows protecting tubes to be subjected to a deliberate pressure check in keeping with their later load. It is not a bursting test to determine the toughness properties of tubular bodies. The testing device needed for this prior art pressure test is complicated and specialized for the testing of protecting tubes.
Another device for testing hollow bodies, especially weapon tubes, is disclosed in DE 2700600 A1. This device is used to determine the pressure resistance, expansion, heating and degree of erosion of the test item. No determination of toughness or testing of fracture behavior is called for. The dynamic pressurization of the tubular test item is carried out by means of propellant gas, hydropulsers or explosive charges, so that devices for these purposes are required. The end regions of the tubular test item are clamped by holders and sleeves in a force-locking and sealing manner.
DE 38 27 080 A1 discloses a process and a device for the dynamic internal pressure testing of hollow bodies, especially protecting tubes. In this process, a dynamic pressure curve relevant to the expected load is produced by means of a piston that closes an opening of the hollow body, and the stresses that occur, particularly the strains, are measured. The hollow body that closable with the piston, together with an elastic intermediate member that interacts with the hollow body in the impact direction, is loaded by means of two colliding masses. Neither this known process nor the disclosed device is suitable for a bursting test. Moreover, the test setup involves expensive apparatus and cannot be set up everywhere.